Add FLAG_UPDATE_CURRENT flag when creating app bubble pending intent

Test: manually
1. open Google Keep in a bubble via stylus button click.
2. confirm the Google Keep drawing activity is shown.
3. close the bubble
4. open Google Keep in a bubble via the keyboard shortcut.
5. confirm the Google Keep text input activity is shown.
Bug: 277925593

Change-Id: I6da71fd976d3739355e2de63f88466ba8350d948